The present invention relates to a system for controlling the position of a bottom pour ladle relative to a plurality of bottom pouring locations. More particularly, the present invention relates to the precision positioning of a crane bridge and the precision positioning of a hoist trolley carried by the crane bridge and is especially useful in a system for semi-automatic precision positioning of an overhead crane dispensing molten steel into a mold configuration.
Although this invention is not limited in its utility to cranes dispensing molten steel, the present invention is particularly well suited for semi-automatic positioning of a teeming aisle hot metal crane in order to preposition the crane bridge and trolley so that the stream of molten metal being poured from the ladle will enter directly into the entry hole of an ingot bottom pour assembly.
In the past, support structure carrying devices, which had to be positioned by relative to a point of operation, were positioned reliance on limit switches. A primary disadvantage inherent in such limit switches is that they are of a binary type (on/off) sensor which does not indicate how close the device is to the point of operation. For example, when such limit switches are employed, an operator of an overhead crane dispensing molten steel will only receive information, regarding the position of the pour location relative to the crane, when the crane is in the pouring position. The operator receives no information regarding the pour location until the crane has reached the pouring position and only at that time will the operator know that the bottom pour ladle is in alignment with the pour location. An obvious disadvantage to a positioning system using limit switches is that the operator will often overtravel the pouring position and be forced to estimate the crane movement necessary to bring the bottom pour ladle into alignment with the pouring position. Miscalculations on the part of the operator may result in the crane running into objects during the positioning of the crane and also misdirecting the stream of molten metal as it is poured, thereby resulting in splashes about the exterior of the mold.
U.S. Pat. No. 4,033,403, issued to Seaton et al., discloses a sensor mechanism which may be mounted on a molten metal pouring machine. The sensing means of Seaton et al. includes a beam which is allowed to contact moving molds or the like, the movement of the beam controlling limit switches and a signal generator. Although the system taught by Seaton et al. does include an override overtravel responsive switch, precise information regarding the position of the ladle relative to the mold is not realized by this system.
Other systems for controlling the position of a ladle relative to a mold or the like include: U.S. Pat. No. 4,144,675 issued to Buhrer; U.S. Pat. No. 4,210,192 issued to Lavanchy et al.; U.S. Pat. No. 4,230,308 issued to Gueguen; and, U.S. Pat. No. 4,084,631 issued to Kunzmann. However, none of the above mentioned patents contemplate the novel sensing and positioning system of the present invention.